In this context, fluid injectors with solid-state actuators are used in particular also in diesel internal combustion engines. The fluid to be metered is often, for example in the case of diesel, supplied to the fluid injector at a feed pressure of up to approximately 2500 bar, and then metered into the respective combustion chamber of the internal combustion engine by means of the fluid injector.
The solid-state actuator comprises an actuator structural unit, and in this regard, with regard to high efficiency, it is important for the actuator structural unit to be preloaded with a force which is dependent on its cross section. Through the provision of a predefined preload force, it is also possible to realize adequate endurance capability.
Furthermore, the actuator structural unit in the fluid injector is generally protected against contact with fuel in order to prevent damage to an insulator or to electrical contact means.
In this context, it is known, for example in the case of an actuator structural unit in the form of a piezo stack, for the preload to be predefined by means of a tubular spring. Sealing is realized by means of a diaphragm which is welded onto an injector body and onto a base plate of the actuator structural unit.